This invention relates generally to aerial vehicles, and relates with particularity to subsonic and supersonic aircraft having an improved safety during takeoff and landing operations and having a reduced supersonic impact wave resistance combined with a better maneuverability. One of the major problems associated with the design of modern fast aircraft is to achieve a satisfactory stability and control of aircraft during low-speed flight. This depends upon the continuously reduced longitudinal distance between the wing and the horizontal tail, which as the final configuration results in the unification of both planes in the one-piece delta-wing. By this process the low-speed flight longitudinal stability and control of the aircraft become worse and worse, and airworthiness and flight safety particularly during takeoff and landing will decrease. If considering improvement possibilities, we first of all have to take the opposite way which is again to increase the longitudinal distance between the wing and the horizontal tail. But since this increased distance is not desirable during high-speed flight, it can be provided temporary and for low-speed flight only. Thus a variable geometry tail unit is brought forth.
In this respect a translating horizontal tail has already been proposed for supersonic aircraft with the primary purpose to counteract the variation of longitudinal stability and control with Mach number. But this proposal was of a general nature only, and without detailed design information (U.S. Pat. No. 3,493,197). The provided dimensional relationship with leading edges of the horizontal tail being equal to the trailing edges of the wings results in an unnecessarily large translating horizontal tail that divided in two separate tail halves represents a tough design job. Also the proposed blunt trailing edges of the wings with leading edges of the horizontal tail in contact with them form a common surface with detrimental lateral grooves which cause supersonic impact waves by which a considerable amount of possible air drag reduction is lost again.
A method of improving the movable tail unit, as contemplated by the present invention, involves a cutout in the trailing edges of the fixed wings positioned symmetrically with respect to the symmetrical axis of the pair of wings, which dimensionally corresponds to the outer dimensions of the movable horizontal tail. Into this cutout is inserted the forward moved horizontal tail during high-speed flight so that the leading edge of the horizontal tail is positioned in front of the trailing edges of the wings. Also the not engaged landing flaps are inserted into the cutout, and on each side of the aircraft the fixed wing, the horizontal tail, and the landing flap together are forming a compact supersonic air foil profile without any lateral groove. This gives a minimum of impact wave resistance with the corresponding saving of propulsion energy.
Accordingly, it is an object of the present invention to provide a new and advanced movable tail unit for supersonic aircraft, to generally improve the airworthiness and safety of aircraft during low-speed flight and particularly during takeoff and landing, and thus save human lifes during these precarious flight operations.
Another object of the present invention is to provide a new and advanced movable tail unit for supersonic aircraft, to generally reduce the air resistance during high-speed flight, and thus save propulsion energy.
Another object of the present invention is to provide a new and advanced movable tail unit for supersonic transport aircraft.
Another object of the present invention is to provide a new and advanced movable tail unit for supersonic fighter aircraft.
According to the present invention, the foregoing and other objects are attained by providing, in a powered aircraft having a fuselage with a vertical tail on its aft end, a movable horizontal tail, a fixed delta-wing or supercritical wings, a fixed horizontal front plane, and jet engines placed on the bottom side of the wings, the trailing edges of the wings have a common cutout positioned symmetrically with respect to the symmetrical axis of the pair of wings. The dimensions of the cutout correspond to the outer dimensions of the one piece movable horizontal tail, and the horizontal tail is inserted into this cutout during high-speed flight. For low-speed flight the horizontal tail is moved rearwards and away from the wings, and forms a separate horizontal tail in the rear of the aircraft. The rearward and forward movement of the horizontal tail is accomplished by means of rails embodied in the rear bottom part of the fuselage, by rollers engaging said rails and being fastened to the horizontal tail by means of brackets, and by control means; and the rearward and forward movements of the horizontal tail are semi-connected with the engagement and disengagement movements of the landing flaps.